1. Field of the Invention
An aspect of the present invention relates to inputting an image into an exposure unit and supplying a recording medium to a transfer unit in an image forming apparatus such as a printer, a copier, and a facsimile, and more particularly, to a method and apparatus to control an image input and a recording-medium supply of an image forming apparatus.
2. Description of the Related Art
An electrophotographic image forming apparatus inputs an image, which is transferred from a host such as a PC, a workstation, or an input from an image input unit such as a copier into an exposure unit such as a laser scanning unit (LSU) or a light emitting diode (LED). The image forming apparatus forms the input image on a photosensitive body such as an electrostatic latent image, and changes the electrostatic latent image into a toner image via a developing unit. Meanwhile, the image forming apparatus accurately moves a recording medium, such as paper, via a recording-medium supply unit and a recording-medium movement adjusting unit, and transfers the above-mentioned toner image on the recording medium, thereby completing a printing operation. In this case, line synchronizing signals or horizontal synchronizing signals, which are line control signals output from the exposure unit, are used to input the image transferred from the host or input from the image input unit into the exposure unit. The line synchronizing signals or the horizontal synchronizing signals are the basis of a starting point per line on a printing image. The image forming apparatus counts the line control signals and controls the start and end of an image input into the exposure unit. Moreover, a timer in the image forming apparatus is used to control a supply time needed for the recording medium to be supplied from the recording-medium supplying unit to the transfer unit. Accordingly, the image input and the recording-medium supply are controlled in different manners. Therefore, in order to print a good-quality image, it is very important to precisely synchronize the time when the image is input into the exposure unit with the time when the recording medium is supplied to the transfer unit. This is particularly required to print a color image because equalizing each color image with each toner image and equalizing the coincident toner image with a recording medium determine printing image quality.
Generally, in order to place an image properly on a recording medium, a monochromatic image forming apparatus synchronizes line control signals outputted from an exposure unit with front end signals of the recording medium supplied from a recording-medium supply unit to control a time when an image is input into the exposure unit. However, since most color image forming apparatuses have a movement path of an image relatively longer than a movement path of the recording medium, the color image forming apparatus synchronizes line control signals with an image input time to control a time when a recording medium is supplied. Moreover, an image input time and a recording-medium supply time are synchronized by a rotation period of a developing unit or a transfer unit.
However, before a printing operation on a first page is completed, a printing operation may be performed on a second page, meaning, a printing operation may be repeatedly and simultaneously performed on two or more pages. This case usually occurs when a path through which the recording medium passes is long. However, even when a toner image of each color is overlapped on another toner image during a color image printing operation, a repeated printing operation may be performed. When the repeated printing operation is performed, if a counter that counts an image input time and a timer that calculates a recording-medium supply time are initialized when each printing operation starts, it cannot be checked whether the recording medium is exhausted from the image forming apparatus after the printing operation is completed. Thus, in order to check whether the recording medium is exhausted from the image forming apparatus, a counter or a timer used for a previous page should not be initialized. Therefore, in order to control the image input time and the recording-medium supply time during the repeated printing operation, a plurality of counters and timers to control the image input and the recording-medium supply should be used. The plurality of counters and timers are synchronized at various points in time. Thus, in order to control the plurality of counters and timers, the image forming apparatus ends up becoming complicated.